Investments

3 Months Ended

Mar. 31, 2019

3. Investments

Available-for-sale securities are carried at fair value, with any unrealized gains and losses reported in comprehensive loss. The amortized cost of debt securities in this category is adjusted for the amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in investment income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in investment income and other, net. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in investment income and other, net. Further, investments in equity securities of certain companies that are subject to holding period restrictions longer than 1 year are carried at fair value, with any unrealized gains or losses reported in other expense, net.

Investments consist of the following:

(in thousands)	March 31, 2019		December 31, 2018
Commercial paper	$	97,490	$	94,572
Corporate debt securities		441,615		544,978
Securities of government sponsored entities		88,874		85,677
Restricted equity securities		56,400		—
Total investments	$	684,379	$	725,227

Investments classified as available-for-sale securities consist of the following:

(in thousands)	Contractual Maturity (in years)	Amortized Cost		Gross Unrealized Gains⁽¹⁾		Gross Unrealized Losses⁽¹⁾			Aggregate Estimated Fair Value
March 31, 2019:
Classified as current assets:
Commercial paper	Less than 1	$	97,517	$	14	$	(41	)	$	97,490
Corporate debt securities	Less than 1		308,363		79		(404	)		308,038
Securities of government-sponsored entities	Less than 1		45,718		65		(21	)		45,762
Total short-term available-for-sale securities		$	451,598	$	158	$	(466	)	$	451,290
Classified as non-current assets:
Corporate debt securities	1 to 2	$	133,179	$	438	$	(40	)		133,577
Securities of government-sponsored entities	1 to 2		42,868		244		—			43,112
Total long-term available-for-sale securities		$	176,047	$	682	$	(40	)	$	176,689
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December 31, 2018:
Classified as current assets:
Commercial paper	Less than 1	$	94,617	$	—	$	(45	)	$	94,572
Corporate debt securities	Less than 1		395,385		—		(1,598	)		393,787
Securities of government-sponsored entities	Less than 1		20,887		8		(55	)		20,840
Total short-term available-for-sale securities		$	510,889	$	8	$	(1,698	)	$	509,199
Classified as non-current assets:
Corporate debt securities	1 to 2	$	151,594	$	66	$	(469	)	$	151,191
Securities of government-sponsored entities	1 to 2		64,676		162		(1	)		64,837
Total long-term available-for-sale securities		$	216,270	$	228	$	(470	)	$	216,028

(1)	Unrealized gains and losses, net of tax, are included in other comprehensive loss.

The following table presents gross unrealized losses and fair value for those available-for-sale investments that were in an unrealized loss position, aggregated by investment category and length of time that individual securities have been in a continuous loss position:

	Less Than 12 Months					12 Months or Greater					Total
(in thousands)	Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses			Estimated Fair Value		Unrealized Losses
March 31, 2019:
Commercial paper	$	31,457	$	(41	)	$	—	$	—		$	31,457	$	(41	)
Corporate debt securities		63,323		(50	)		174,206		(394	)		237,529		(444	)
Securities of government-sponsored entities		—		—			10,979		(21	)		10,979		(21	)
Total	$	94,780	$	(91	)	$	185,185	$	(415	)	$	279,965	$	(506	)
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December 31, 2018:
Commercial paper	$	51,927	$	(45	)	$	—	$	—		$	51,927	$	(45	)
Corporate debt securities		274,696		(746	)		234,798		(1,321	)		509,494		(2,067	)
Securities of government-sponsored entities		4,999		(1	)		10,947		(55	)		15,946		(56	)
Total	$	331,622	$	(792	)	$	245,745	$	(1,376	)	$	577,367	$	(2,168	)

At each reporting date, we perform an evaluation of impairment to determine if any unrealized losses are other-than-temporary. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition of the issuer, and our intent and ability to hold the investment until recovery of the amortized cost basis. We intend and have the ability to hold our investments in unrealized loss positions until their amortized cost basis has been recovered. Further, based on our evaluation, we determined that unrealized losses were not other-than-temporary at March 31, 2019 and December 31, 2018.